Java || Snippet – How To Send Text Over A Network Using Socket

January 08, 2014 admin No comments

The following is sample code which demonstrates the use of the “socket” function call for interprocess communication over a network.

The following example demonstrates a simple network application in which a client sends text to a server, and the server replies (sends text) back to the client.

Note: The server program must be ran before the client program!

=== 1. SERVER ===





		
		
			IPC Networking - Server
			
Java
			
			// ============================================================================
//   Author: K Perkins
//   Date:  Jan 8, 2014
//   Taken From: http://programmingnotes.org/
//   File: Server.java
//   Description: This program implements a simple network application in 
//     which a client sends text to a server and the server replies back to the
//     client. This is the server program, and has the following functionality:
//       1. Listen for incoming connections on a specified port.
//       2. When a client tries to connect, the connection is accepted.
//       3. When a connection is created, text is received from the client.
//       4. Text is sent back to the client from the server.
//       5. Close the connection and go back to waiting for more connections.
// ============================================================================
import java.io.*;
import java.net.*;
import java.util.Date;

// Compile & Run
// javac Server.java
// java Server 1234

class Server
{
    // the port on which to listen 
    protected int listenPort;

    // the initialization constructor		 
    public Server(int port)
    {
	    // save the listening port 
	    listenPort = port;
    }// end of Server

    // executes the main server loop		 
    public void mainServerLoop() throws Exception
    { 
	    // create a listening socket in the specified port.	     
	    ServerSocket listenSock = new ServerSocket(this.listenPort);

	    // keep servicing the clients 
	    while(true)
	    {
		    System.out.println("nWaiting for someone to connect..");
		    
		    // accept the incoming connection from the client 
		    Socket communicationSocket = listenSock.accept();

		    // the client-to-server stream 
		    BufferedReader inFromClient =
			    new BufferedReader(new InputStreamReader(
			    communicationSocket.getInputStream()));

		    // the server-to-client stream 
		    DataOutputStream outToClient = 
			    new DataOutputStream(communicationSocket.getOutputStream());

		    // display misc. IPC information
		    System.out.println("n(SRCIP=" + communicationSocket.getInetAddress()+ 
		    ", SRCPORT="+communicationSocket.getPort() + ") "+"(DESTIP="+ 
		    communicationSocket.getLocalAddress()+", DESTPORT="+
                 	 communicationSocket.getLocalPort()+")");
                 	 
		    // receive a string from the client 
		    String clientMsg = inFromClient.readLine();
		    System.out.println("nRECEIVED: ""+clientMsg+"" from the client");
		
		    // instantiate a date class: used for obtaining the current time
		    Date date = new Date();

		    // send the current time and date to the client 
		    System.out.println("nSENDING: ""+date.toString()+"" to the client");
		    outToClient.writeBytes(date.toString());

		    // close the connection to the client 
		    communicationSocket.close();
	    }	
    }// end of mainServerLoop		

    public static void main(String[] args)
    {
	    // make sure the port number is provided 
	    if(args.length != 1)
	    {
		    System.out.println("USAGE: java Server <SERVER PORT #>");
	    }
	    else
	    {
		    // create an instance of the server class 
		    Server server = new Server(Integer.parseInt(args[0]));
		
		    try
		    {
			    // start receiving client connections 
			    System.out.println("nServer started!");
			    server.mainServerLoop();
		    }
		    catch(Exception e) { e.printStackTrace(); }
	    }
    }// end of main
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//   Author: K Perkins
//   Date:  Jan 8, 2014
//   Taken From: http://programmingnotes.org/
//   File: Server.java
//   Description: This program implements a simple network application in 
//     which a client sends text to a server and the server replies back to the
//     client. This is the server program, and has the following functionality:
//       1. Listen for incoming connections on a specified port.
//       2. When a client tries to connect, the connection is accepted.
//       3. When a connection is created, text is received from the client.
//       4. Text is sent back to the client from the server.
//       5. Close the connection and go back to waiting for more connections.
// ============================================================================
import java.io.*;
import java.net.*;
import java.util.Date;
 
// Compile & Run
// javac Server.java
// java Server 1234
 
class Server
{
    // the port on which to listen 
    protected int listenPort;
 
    // the initialization constructor		 
    public Server(int port)
    {
	    // save the listening port 
	    listenPort = port;
    }// end of Server
 
    // executes the main server loop		 
    public void mainServerLoop() throws Exception
    { 
	    // create a listening socket in the specified port.	     
	    ServerSocket listenSock = new ServerSocket(this.listenPort);
 
	    // keep servicing the clients 
	    while(true)
	    {
		    System.out.println("nWaiting for someone to connect..");
		    
		    // accept the incoming connection from the client 
		    Socket communicationSocket = listenSock.accept();
 
		    // the client-to-server stream 
		    BufferedReader inFromClient =
			    new BufferedReader(new InputStreamReader(
			    communicationSocket.getInputStream()));
 
		    // the server-to-client stream 
		    DataOutputStream outToClient = 
			    new DataOutputStream(communicationSocket.getOutputStream());
 
		    // display misc. IPC information
		    System.out.println("n(SRCIP=" + communicationSocket.getInetAddress()+ 
		    ", SRCPORT="+communicationSocket.getPort() + ") "+"(DESTIP="+ 
		    communicationSocket.getLocalAddress()+", DESTPORT="+
                 	 communicationSocket.getLocalPort()+")");
                 	 
		    // receive a string from the client 
		    String clientMsg = inFromClient.readLine();
		    System.out.println("nRECEIVED: ""+clientMsg+"" from the client");
		
		    // instantiate a date class: used for obtaining the current time
		    Date date = new Date();
 
		    // send the current time and date to the client 
		    System.out.println("nSENDING: ""+date.toString()+"" to the client");
		    outToClient.writeBytes(date.toString());
 
		    // close the connection to the client 
		    communicationSocket.close();
	    }	
    }// end of mainServerLoop		
 
    public static void main(String[] args)
    {
	    // make sure the port number is provided 
	    if(args.length != 1)
	    {
		    System.out.println("USAGE: java Server <SERVER PORT #>");
	    }
	    else
	    {
		    // create an instance of the server class 
		    Server server = new Server(Integer.parseInt(args[0]));
		
		    try
		    {
			    // start receiving client connections 
			    System.out.println("nServer started!");
			    server.mainServerLoop();
		    }
		    catch(Exception e) { e.printStackTrace(); }
	    }
    }// end of main
}// http://programmingnotes.org/

=== 2. CLIENT ===





		
		
			IPC Networking - Client
			
Java
			
			// ============================================================================
//   Author: K Perkins
//   Date:  Jan 8, 2014
//   Taken From: http://programmingnotes.org/
//   File: Client.java
//   Description: This program implements a simple network application in 
//     which a client sends text to a server and the server replies back to the
//     client. This is the client program, and has the following functionality:
//       1. Establish a connection to the server.
//       2. Send text to the server.
//       3. Recieve text from the server.
//       4. Close the connection and exit.
// ============================================================================
import java.io.*;
import java.net.*;

// Compile & Run
// javac Client.java
// java Client localhost 1234

class Client
{
	// the server IP address  
	protected String svrIpAddr;
	
	// the server port number  
	protected int svrPort;
	
	/* the initialization constructor
	 * @param ipAddr - the IP address of the server
	 * @param port - the port on which the server is listening
	 */
	public Client(String ipAddr, int port)
	{
		// save the server's IP address and port number  
		svrIpAddr = ipAddr;
		svrPort = port;
	}// end of Client
	
	// connects to the server 	  
	public void connectToServer() throws Exception
	{
		// the message to send to the server  
		String msgForServer = "Server, what time is it?";
		
		// the string to store the date and time to be received from the server  
		String dateAndTime = null;
		
		// create a socket and use it for connecting to the server   
  		Socket clientSocket = new Socket(svrIpAddr, svrPort);
		
		// the client-to-server stream  
		DataOutputStream outToServer = 
				new DataOutputStream(clientSocket.getOutputStream());

		// the server-to-client stream  
		BufferedReader inFromServer = 
			new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
		
		// write the string to the server 
		System.out.println("nSENDING: ""+msgForServer+"" to the servern"); 	
		outToServer.writeBytes(msgForServer+"n");
		
		// get the date and time from the server  
  		dateAndTime = inFromServer.readLine();
		
		// print the date and time received from the server  
		System.out.println("RECEIVED: ""+dateAndTime+"" from the servern");
		
		// close the socket  
		clientSocket.close();
	}// end of connectToServer
	
	public static void main(String args[])
	{
		// check the command line arguments  
		if(args.length < 2)
		{
			System.err.println("n** ERROR NOT ENOUGH ARGS!n"
			    +"USAGE: Client <SERVER IP> <SERVER PORT #>n");
		}
		else
		{			
			// instantiate the client class  
			Client client = new Client(args[0], Integer.parseInt(args[1]));
			
			try
			{
				// connect to the server  
				client.connectToServer();	
			}
			catch(Exception e) { e.printStackTrace(); }
		}
	}// end of main
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//   Author: K Perkins
//   Date:  Jan 8, 2014
//   Taken From: http://programmingnotes.org/
//   File: Client.java
//   Description: This program implements a simple network application in 
//     which a client sends text to a server and the server replies back to the
//     client. This is the client program, and has the following functionality:
//       1. Establish a connection to the server.
//       2. Send text to the server.
//       3. Recieve text from the server.
//       4. Close the connection and exit.
// ============================================================================
import java.io.*;
import java.net.*;
 
// Compile & Run
// javac Client.java
// java Client localhost 1234
 
class Client
{
	// the server IP address  
	protected String svrIpAddr;
	
	// the server port number  
	protected int svrPort;
	
	/* the initialization constructor
	 * @param ipAddr - the IP address of the server
	 * @param port - the port on which the server is listening
	 */
	public Client(String ipAddr, int port)
	{
		// save the server's IP address and port number  
		svrIpAddr = ipAddr;
		svrPort = port;
	}// end of Client
	
	// connects to the server 	  
	public void connectToServer() throws Exception
	{
		// the message to send to the server  
		String msgForServer = "Server, what time is it?";
		
		// the string to store the date and time to be received from the server  
		String dateAndTime = null;
		
		// create a socket and use it for connecting to the server   
  		Socket clientSocket = new Socket(svrIpAddr, svrPort);
		
		// the client-to-server stream  
		DataOutputStream outToServer = 
				new DataOutputStream(clientSocket.getOutputStream());
 
		// the server-to-client stream  
		BufferedReader inFromServer = 
			new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
		
		// write the string to the server 
		System.out.println("nSENDING: ""+msgForServer+"" to the servern"); 	
		outToServer.writeBytes(msgForServer+"n");
		
		// get the date and time from the server  
  		dateAndTime = inFromServer.readLine();
		
		// print the date and time received from the server  
		System.out.println("RECEIVED: ""+dateAndTime+"" from the servern");
		
		// close the socket  
		clientSocket.close();
	}// end of connectToServer
	
	public static void main(String args[])
	{
		// check the command line arguments  
		if(args.length < 2)
		{
			System.err.println("n** ERROR NOT ENOUGH ARGS!n"
			    +"USAGE: Client <SERVER IP> <SERVER PORT #>n");
		}
		else
		{			
			// instantiate the client class  
			Client client = new Client(args[0], Integer.parseInt(args[1]));
			
			try
			{
				// connect to the server  
				client.connectToServer();	
			}
			catch(Exception e) { e.printStackTrace(); }
		}
	}// end of main
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

The following is sample output.

SERVER OUTPUT:

Server started!
Waiting for someone to connect.. (SRCIP=/127.0.0.1, SRCPORT=46608) (DESTIP=/127.0.0.1, DESTPORT=1234) RECEIVED: "Server, what time is it?" from the client
SENDING: "Wed Jan 08 18:07:15 PST 2014" to the client

CLIENT OUTPUT:

SENDING: "Server, what time is it?" to the server
RECEIVED: "Wed Jan 08 18:07:15 PST 2014" from the server

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Posted in: Console, Java, Java, Snippets Tags: cpsc 471, ipc, networking, socket

Java || Snippet – How To Send Text Over A Network Using Socket

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